Generally, an electronic device is equipped with an input device for inputting contents of a predetermined work to execute it.
For example, the input device includes a keyboard of a household computer, input buttons of a mobile phone or the like.
Such an input device is usually configured of a button type in which buttons are hit or depressed.
In this button type input device, there is a limitation in reducing the size of the button, and hence it does not follow a trend toward miniaturized electronic devices.
Taking a computer keyboard as an example, the keyboard usually has 107 input keys. Even if overlapped input keys are omitted, there are 89 input keys.
A user strikes the keyboard using all the fingers of his or her both hands in order to input characters, numerals, symbols, etc.
When a user utilizes the computer, it is important to rapidly strike the keyboard in order to input commands.
If the size of the keyboard is reduced, however, two or more input keys can be depressed by one finger only. As a result, there is a limitation in miniaturizing the size of the keyboard. This does not follow a trend in which a monitor and a CPU are miniaturized so that they can be portable.
In order to solve this problem, there was disclosed Korean Patent Application No. 10-2001-0014923 (Mar. 22, 2001) entitled “Handheld Type Keypad Device That Can Be Manipulated By One Finger” in which a somewhat small input keys are arranged circularly.
In the above device, however, in order to secure a space between the input keys, the size of the input key is made a little small and the input keys are only arranged circularly. Thus, there is a limit in miniaturizing the input device.
Furthermore, even the miniaturization of the above degree does not follow a current trend toward size reduction of electronic devices.